This invention relates to compositions for sealing calcified tissue substrates to inhibit infection and promote subsequent restorative material bonding; in particular, the invention is tailored to dentinal tubules, in order to prevent dentinal hypersensitivity and further to promote effective bonding of subsequent restorative dental materials such as amalgams, composites, resins and cementitious materials.
Dental caries are a common disease of modem humankind. The treatment of dental caries involves the removal of the carious lesion by a number of means including mechanical drilling and light ablation. The ensuing removal of dentin brings the dental nerve endings contained within the pulp into proximity with the mouth. Filling the resulting cavity in order to isolate the nerve endings leaves the tooth susceptible to thermal hypersensitivity via thermal conduction through the filling as well as bacterial infection. Bacterial colonization of the filled cavity induces further caries formation and hypersensitivity.
Currently, polymeric resinous materials are widely used to fill cavities, as well as in cosmetic dentistry and corrective dental structures including brackets, braces, veneers, onlays, crowns, and the like. In adhering dental structures to tooth enamel, there are minor problems with thermal or bacterial hypersensitivity.
In contrast, when the dentin of a tooth is exposed as a result of cervical erosion or tooth decay, changes occur in the physical structure of the dentin. Whereas tooth enamel is a densified, nonporous substance, dentin is characterized by a porous structure containing thousands of dentinal tubules. The dentinal tubules extend outward from the tooth pulp and terminate at or before the tooth enamel. These tubules contain pressurized pulp fluid which seeps from the pulp when the ends of the tubules are exposed. Collagen fibers are also associated with the tubules.
Typically, neither cervical erosion nor drilling of dentin directly exposes the ends of the dental tubules. Cervical erosion surfaces are characterized by irregularities and hemispherical protrusions. The dentinal tubules are mostly filled with inorganic material although some maintain openings of various sizes. Drilling of dentin creates a debris field which is characterized by weakened and cracked dentin. Since the debris field is structurally unsound, adhering a restorative material thereto creates a weak filling.
The cleaning of dentin prior to bonding a material thereto is thus highly advantageous. Typically, acid etching is used to decalcify the surface dentin and enlarge the openings of the tubules. Acid etching leaves behind the protruding collagen fibers that are associated with the dentinal tubes. Chelating agents such as EDTA are known to help dissolve calcified deposits associated with a dentinal tubule opening. These collagen fibers represent a substrate for bacterial colonization as well as a hydrophilic surface for the bonding of a polymeric resinous material. The acid etching solution is typically a 20-50% by weight solution of phosphoric acid, but also includes citric and nitric acids.
A number of facing preparations are currently in use to seal and disinfect a dentin surface following acid etching. These preparations typically include a monomeric resin capable of cross linking to the collagen fibers. Glutaraldehyde (GLUMA, Heraeus Kulzer, Inc.) and benzalkonium chloride (Healthdent, Inc.) are added as antimicrobials. These prior art antimicrobials are limited in their efficacy. Glutaraldehyde polymerizes in water and thereby the effective dosages decrease. Furthermore, glutaraldehyde is a known irritant as well as antiseptic and thereby may induce the dental hypersensitivity which the facing preparation is designed to prevent. Benzalkonium chloride is a potent antimicrobial yet is incompatible with anionic detergents such as soap, as well as with nitrates. While the benzalkonium cation is electrically attracted to dentin, stearic considerations prevent optimal interactions between the radical and dentinal tubules.
The present invention provides a facing preparation composition containing a polymerizable resin and an antimicrobial agent having the formula: 
where R1 is a hydrocarbon having between 1 and 16 carbon atoms, n is an integer between 1 and 8 inclusive, R2 is selected from the group consisting of halophenyl and 2-ethylhexyl. The antimicrobial agent is delivered in the form of an organic salt, with the anionic species illustratively selected from: acetate, gluconate, propionate, and acrylate. Optionally, a solvent is also provided to promote diffusion of the other composition components into a substrate. Solvents operative in the present invention illustratively include: methanol, water, acetone, methyl ethyl ketone, and isopropanol.
The facing preparation composition also includes 0.1 to 20% by weight glutaraldehyde as a secondary and synergistically acting antimicrobial. Alternatively, a chelating agent is present in the facing preparation in order to complex calcified deposits associated with dentinal tubule openings so as to prepare a clean dentinal tubule bonding surface.
An antimicrobial oral rinse contains the antimicrobial agent present at greater than 0.2% by weight in a buccal cavity compatible solvent containing a chelating agent and excluding the polymerizable resin of the facing preparation composition.